James Riddet, an attorney representing Milco International Inc., said, "I can tell you there's a federal grand jury investigation and that's all." U.S. policy forbids exportation of the devic es, called krytrons, without State Department permission.

The attorney said the company's owner, Richard K. Smyth, retained him about three months ago to represent the company in the federal proceedings. Smyth, who left for Europe with his family last weekend, could not be reached to comment on the federal inquiry.

Smyth, his wife Emilie, their sons, daughters-in-law and grandchildren, are not due back until May 28, according to an independent consultant working alone in the Milco office Wednesday.

"They told me it was a pleasure trip with business mixed in," said the consultant, who was hired by Smyth about a week ago to work on an engineering study and who agreed to be interviewed on the condition that he not be identified.

Meanwhile, United Press International reported that the State Department and Israeli sources in Washington both denied Wednesday that the United States has asked to inspect Israel's nuclear facilities to check whether U.S.-made timing devices are being used for atomic bomb triggers or were sent to a third country.

A State Department official denied a Washington Post report that the United States asked for such an inspection to account for the krytrons. "No such request was made by the American government," the official said.

State Department spokesman Edward P. Djerejian said that Israel "has been cooperative in our investigation on this matter."

An Israeli source in Washington agreed. "There was never a demand (by Washington) to inspect nuclear facilities" in Israel, he said. "We are fully cooperating with the Americans and they are quite happy with our cooperation."

Israel "might be requested to return" any unused krytrons to the United States, Israeli sources said.

The Israeli Defense Ministry acknowledged Sunday that it acquired several krytrons between 1979 and 1983 and said it still has a stockpile of the timers. It has used the krytrons in connection with research and development for conventional weapons, lasers and medical equipment, the Israeli sources said.

The ministry denied that any of the devices have been passed on to other countries.

Israel long has been named as one of several countries capable of building nuclear weapons. It has permitted U.S. officials to inspect its major atomic facility, at Dimona in the Negev desert, which was built with French help in 1957.

Newsweek magazine said that up to 600 krytrons were sent to Israel illegally. The Israeli government, the sources said, was not aware that the devices may have been been smuggled to Israel in violation of the U.S. Atomic Energy Act and the Export Administration Act.

"We acknowledge that the units have been used in defense-related industries," one source said. "We didn't know they were smuggled, since they are easy to obtain. They cost only $75 and they are easy to acquire."

A man who claimed to have worked for Milco in 1981 said in an interview Wednesday that Milco regularly shipped a variety of electronic equipment to Israel and Europe.

"A guy manned the Teletype all day," said the former employee, who asked not to be identified.

Immediate Shipment

He claims to have frequently seen equipment from krytron manufacturer EG&G Inc. of Wellesley, Mass., delivered to Milco and shipped out immediately.

In 1981, Smyth owned a short-lived computer company called Computerm. Smyth's son, Randy, is believed to own a sailboat business. The former employee said another son, David, worked on research and development projects with the elder Smyth. A third son, whose name he could not recall, handled Milco's export business. He said Richard Smyth has a doctorate in electrical engineering and served as a vice president at Rockwell International Corp., but a Rockwell spokesman said he could not confirm or deny whether Smyth had been employed there.

A woman answering the phone at the Randy Smyth residence in Huntington Beach late Wednesday refused to identify herself. "I'm not going to say anything," she said.